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OCEAN ELECTRONIC NAVIGATIONAL AIDS 



Figure 2-5. — A modern radio direction finder installed aboard ship. 



Cape Cod Radiobeacon, Massachusetts, and Point Arguello Radiobeacon, 

 California, are high-power class A radiobeacons which have effective ranges 

 of about 400 miles. 



The most powerful sound-in-air fog signals under favorable conditions may 

 be heard at distances of 10 to 15 miles, but their ordinarily dependable range 

 is not over 5 miles, and, under unfavorable conditions, they are lost at dis- 

 tances shorter than this. The coast lights are visible for 15 to 20 miles 

 and large lighted buoys for about 9 to 12 miles. It is therefore readily seen 

 that the radiobeacons have a much greater range of usefulness, in fog as well 

 as in clear weather. This is illustrated by the fact that on the outside 

 Atlantic coast of the United States, north of Cape Hatteras, there are but 19 

 radiobeacons. This length of coast requires five times this number of sound 

 fog signals, and they are effective over only 2 percent of the area served by 

 the radiobeacons. The same length of coast has 150 outside lights. 



In order to lessen interference, the power of radiobeacons is limited to that 



